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Man initial idle not in sync

Discussion in 'Engines' started by Danvilletim, Dec 30, 2020.

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  1. Danvilletim

    Danvilletim Senior Member

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    2012 Man 800 hp. On start port is 630 and starboard is 600. Sync button doesn’t work at that low rpms. Is initial idle adjustable?
  2. NYCAP123

    NYCAP123 Senior Member

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    Are those readings at the helm gauges or at the motor?
  3. mapism

    mapism Senior Member

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    The only 800hp MAN engines available in 2012 were the CRM R6, which normally were equipped with the MMDS displays.
    If this is the case, the reading should be pretty solid regardless of the placement.

    But personally, I would still waste 15 bucks for a chinese laser tacho, which are amazingly accurate.
    Not that I'm expecting the MMDS readings to be wrong, but it doesn't hurt to check.

    Anyhow, to try to answer the OP question, I believe that adjustments (if feasible) require the dealer diagnostic system.
  4. Capt Ralph

    Capt Ralph Senior Member

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    Yes, I believe the idle is still computer controlled.
    My BD subscription just expired.
    If there is a long lag time and they do sync up, it may be sensor fault issue. Still, needs a proper tech plugged in.
    I remember up to 10-15 seconds before MANs came to set idle when cold. Maybe 5 seconds when warm.

    Like the CAT 3406, I am a big fan of the MAN in line 6. Lots of HP can still be achieved here. Minimal crank distortion means a long life engine.
    Last edited: Dec 30, 2020
  5. Danvilletim

    Danvilletim Senior Member

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    Reading is at helm. The biggest issue is the thumping noise of them being out of sync. More annoying than anything.
  6. mapism

    mapism Senior Member

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    CR, as I recall the sync doesn't engage at all, under 1000 (or whatever) rpm.
  7. Capt J

    Capt J Senior Member

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    Could be the start of a control head issue. Put them in sync at idle speed, what RPM's do they read then?

    Mapism- On the common rail mans, they all came with Rexroth controls (as far as I know). The only way to put them into synch is at idle in gear. Synch is then done from the ECM's and you only advance the starboard stick/throttle and computer brings both up. They synch anywhere from dead idle on up.
  8. mapism

    mapism Senior Member

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    When you run each of them alone, are they running just fine?
    If yes, even if 30rpm isn't exactly negligible, I'd be tempted to not bother...
  9. Capt Ralph

    Capt Ralph Senior Member

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    Not using engine sync. Computer sets the idle speed.
    When you come in / out of gear, it may take up to 5 seconds (warm) before the engines settle on idle. If they are off, ya got call the kid with the lap-top.
  10. mapism

    mapism Senior Member

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    Ok, I understood that by lag time you meant after turning sync on.
  11. Capt Ralph

    Capt Ralph Senior Member

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    Thumping from the exhaust or really out of sync with each other.
    My Bert thumps at idle under certain hull levels (exhaust ports level or down) that strums in my ears.
    I remember a Nova Tech 80 that drove me crazy with under hull exhaust thrumming at idle.
  12. mapism

    mapism Senior Member

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    I would have sweared that the engine sync function is only available above a somewhat higher than idle rpm, regardless of whether gear is engaged or not. But it's been a while since I helmed a CRM powered boat - If you say so, I take your word for it.
  13. Capt Ralph

    Capt Ralph Senior Member

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    Not sure if you can put these controls in sync at un-loaded idle. Never had to try.
  14. Capt J

    Capt J Senior Member

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    No, have to be in gear at idle speed to access synch. Unloaded idle does not allow synch. OP's boat is of the ERA that the MAN controls had issues with the pots moving around inside the control housing as they go bad, that is my guess as to why one engine idles at 630 rpms, it's seeing a slight throttle signal when put in gear. You can tell the new style controls from the old style, the difference is in the large hole at the base of the shifter.
  15. Capt Ralph

    Capt Ralph Senior Member

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    Ah, the later kinky (rotary) shifters. I know what you mean here.
    BUT, the OP says on start. Is this starting the engines and at idle, out of gear??
  16. Capt J

    Capt J Senior Member

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    They'll do the same thing at idle out of gear. One way to check is to scroll over to the load/throttle page, make sure both of them are reading the same throttle percentage.
  17. Capt Ralph

    Capt Ralph Senior Member

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    Good note here.
    Never looked at idle load before.
    I'll have to check this my self if I'm ever on another MAN boat.
    I recall on some other post we talked about alternator loads affecting idle speeds. Wonder if this is could be an issue here also.

    Probably need more info from the OP on all of our thoughts.
  18. Sea Gull

    Sea Gull Member

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    PTO for hydraulics is another place to look. If that engine is driving a running pump, it would increase rpm to handle the load.
  19. Capt J

    Capt J Senior Member

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    Load could be another one. OP could put them both in reverse in a safe area and see if it does it in reverse, and also look at the throttle % in gear in forward (not load %). I still think it's in the throttle, but a MAN tech could come out and hook up their laptop and figure it out in less than 2 hours.

    Arnesons, at hull speed or less (or any speed really), its real easy to load one motor more than the other. I ran a 59' Baia with DDEC's and unless the drives were 100% up, you had to put them all of the way up, then hold the up levers another 5 seconds after the gauges indicated they were all of the way up to get that extra 1" (we measured it). Putting them in gear they'd drop from 600 rpms to 440 rpms and black smoke like crazy and you'd have no throttle whatsoever. It made docking a really planned and spirited adventure if you had to use reverse at all. But if you had the drives 100% and the boat wasn't heavy on fuel, they'd suck just enough air to slip a little and then the governors could carry the load.
  20. Danvilletim

    Danvilletim Senior Member

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    We have a single twin disc control. Great Lakes power helped w a bad sync sensor ( they are awesome as they just walked be through it). They said I had to recalibrate the head unit by holding down the station select button. But there isn’t one that I can find.

    It not a big deal so I can live with it until next Service.